50cc Carbon Fiber for ULTEM Filament CFFCarbon Fiber CFR (Continuous Fiber Reinforcement) Spools. The backbone of aluminum strength composite parts Carbon Fiber is Markforgeds unique, ultra high strength Continuous Fiber when laid into a Composite Base material like Onyx, it can yield parts as strong as 6061 T6 Aluminum. Its extremely stiff and strong, and can be automatically laid down in a wide variety of geometries by Markforged 3D printers. Carbon Fiber compatible with ULTEM 9085